Search for a trainer who has some kind of proficiency in this particular field. He should have a trainer's degree from a recognized University or relevant past experience. In case of online personal trainers check and authenticate the certificates he produces online. Also, find out whether your potential trainer keeps updating his knowledge about training so as to provide clients with new techniques in training.
You should know whether a trainer has any working experience or not. It is preferable if he has at least five years of experience. He should also have some sort of insurance cover.
Discuss with your potential trainer about his specialties. Check if he is an expert in orthopedic rehabilitation or has an athletic training background. Find out as much as possible. Ask for some references. Though he may be reluctant to name a person there is no harm in trying.
Try to know the success rate of your personal trainer. A personal trainer should be able to motivate and communicate with you. He should inspire you to achieve your training goals. Also, know whether you are compatible with him or feel uncomfortable in his company. Check this out so as not to repent later.
Do not get deceived by looks of a personal trainer. It is not necessary that a well-built muscular person can be a good personal trainer too. Remember, you will be training alone with him. So, other than the physical traits, he should have a good communicating power and should be able to put you at ease. It is different when he is training many people. Training at a personal level involves an altogether different strategy.
Know how much you would be required to pay him as fees. Check out the going rates at gyms and health clubs. These memberships are cheaper as compared to fees charged by personal trainers. Compare fees charged by your personal trainer with others in the same line of work. Also, if he has his own gym, then the rate may be less as compared to what he is likely to charge if he visits your place as per your schedule.
Keeping these simple facts in mind will go a long way in helping you select the best personal trainer who will design a training schedule keeping in mind your health and training goals.